Approach flow system for papermaking machine



Nov. 7, 1967 o s 3,351

APPROACH FLOW SYSTEM FOR PAPER MAKING MACHINE Filed Aug. 5, 1964 4Sheets-Sheet l KA'SIMIR LOPAS A TTOR/VE rs Nov. 7, 1967 K. LOFASAPPROACH FLOW SYSTEM FOR PAPER-MAKING MACHINE 4 Sheets-Sheet 2 FiledAug. 5, 1964 INVENTOR. KASIMIR LOPAS his A TTOfi/VEYS K. LOPAS 3,351,522

APPROACH FLOW SYSTEM FOR PAPER-MAKING MACHINE Nov. 7, 1967 Filed Aug. 5,1964 4 Sheets-Sheet 5 m l hv INVENTOR. KASiMIR LOPAS Em, J Wfl ATTORNEYShis K. LOPAS 3,351,522 APPROACH FLOW SYSTEM FOR PAPER-MAKING MACHINENov. 7, 1967 4 Sheets-Sheet 4 Filed Aug. 5, 1964 INVENTOR.

KASI MIR LOPAS W- PM @W k gww his A TTORNEYS United States Patent3,351,522 APPROACH FLOW SYSTEM FUR PAPER- MAKING MACHINE Kasimir Lopas,Stamford, Conn., assignor to THEME,

Incorporated, New York, N.Y., a corporatron of New York Filed Aug. 3,1964, Ser. No. 387,133 11 Claims. (Cl. 162-637) This invention relatesto paper-making methods and apparatus and, more particularly, to noveland highly effective methods of and apparatus for delivering to apaper-making machine a paper stock under conditions of uniformconsistency and velocity.

It is of the utmost importance that the paper stock delivered to apaper-making machine be of uniform consistency and velocity at theslice. Variations in the consistency or velocity of a paper stock at theslice result in variations from point to point in the characteristics ofthe paper produced. Such uneven characteristics con stitute a seriousimperfection in the paper, particularly when the paper is intended foruse in a process such as the printing of magazines and books.

The maintenance of uniformity of stock consistency and velocity at theslice is extremely difficult. The stock supplied from a vat or otherstorage means to the flow system may not be perfectly homogeneous.Moreover, turns or bends in the ductwork forming typical stockflowsystems result in non-uniform velocity of the stock as it leaves theturns. For these and other reasons, the stock as it exits from the sliceand onto the foraminous belt of the paper-making apparatus is never ofcompletely uniform consistency or velocity, either spatially i.e.,across the face of the slice-or temporallyi.e., from one moment to thenext.

An object of the present invention is to remedy the diflicultiesreferred to above. In particular, an object of the present invention isto provide a stock-flow system which provides a flow of stock ofsubstantially uniform consistency and having a substantially uniformvelocity at all points of a given cross-sectional area of the flowsystem, such as the cross-sectional flow area at the slice, and frommoment to moment. Another object of the invention is to provide meansfor changing the direction of flow of a stream of stock so that thestock emerges from the change of direction having a uniform velocity atall points across a cross-section of the stock.

These and other objects are attained in accordance with a representativeembodiment of the invention by a recirculating loop and a tapered-flowheader which may be used separately or in combination. The recirculatingloop delivers stock from a source to the paper-forming apparatus over aplurality of paths of unequal length. The tapered-flow header has across-sectional flow area which decreases in a first direction of flowfrom a maximum value to a minimum value, the maximum and minimum valuesbeing so related to each other and to energy losses due to friction thatthe horizontal components of the pressure gradient in the paper stocknormal to the second direction at the origin of movement of the stock inthe second direction substantially vanish and the components of thepressure gradient in the paper stock in the second direction at theorigin of movement of the stock in the second direction are ofsubstantially equal magnitude. Specially-designed stock-flow guide vanesmay be mounted in the tapered-flow header to facilitate turning of thepaper stock from flow in the second direction at substantially uniformvelocity across a cross section of the flow in the second direction toflow in a third direction at substantially uniform velocity across across-section of the flow in the third direction.

An understanding of further aspects of the invention 3,351,522 PatentedNov. 7, 1967 may be gained from a consideration of the followingdetailed description of several representative embodiments thereof inconjunction with the accompanying figures in the drawings, of which:

FIG. 1 is an end elevational view, partly in phantom, of apparatusconstructed in accordance with the invention;

FIG. 2 is a sectional vew taken substantially along the line 2-2 of FIG.1 and looking in the direction of the arrows;

FIG. 2A is a side sectional view similar to FIG. 2 but showing amodification in accordance with the invention of a portion of theapparatus of FIG. 2;

FIG. 3 is a plan view of one form of tapered-flow header constructed inaccordance with the invention;

FIG. 4 is a view taken substantially along the line 44 of FIG. 3;

FIG. 5 is a plan view of a combination in accordance with the inventionof a recirculating loop and the taperedfiow header shown on a largerscale in FIG. 3;

FIG. 6 is a fragmentary view of a portion of FIG. 5;

FIG. 7 is a plan view of another combination of tapered-flow header andrecirculating loop constructed in accordance with the invention;

FIG. 8 is an enlarged view taken substantially along the line 88 of FIG.7 and looking in the direction of the arrows; and

FIG. 9 is a view taken substantially along the line 9-9 of FIG. 8 andlooking in the direction of the arrows.

Throughout the present disclosure, the word paper is used in a genericsense to include paper, paperboard, and similar products.

FIGS. 1 and 2 show an exemplary embodiment of apparatus constructed inaccordance with the invention. Those figures show lower and upper breastrolls 10, 12 about which are trained lower and upper Fourdrinier wires14, 16 or other permeable belts adapted to transport a web of paperstock and effect removal of water therefrom to form a web of paper. Thelower breast roll 10 is rotatably mounted on a shaft 13, and the upperbreast roll 12 is also rotatably mounted on a shaft (not shown). Thebreast rolls 10, 12 may be foraminous or solid and may be mounted invarious positions with respect to each other.

Paper stock is delivered by a flow system designated generally by thenumeral 20 through a slice 22 which ejects the stock between the wires14, 116 as a wide flat layer lying in a plane normal to the plane of thefigure. The breast rolls 10, 11 rotate in the directions indicated bythe arrows at speeds which are typically substantially equal to thespeed with which the stock is ejected from the slice 22. Water isexpressed from the stock through the wires 14, 16 to form a web ofpaper.

The present invention relates not to the paper-making apparatusdownstream of the slice 22 but to the flow system 20. In accordance withthe invention, a source of paper stock such as a supply-flow channel 24(FIG. 1) forms a fluid-conducting connection 26 with a recirculatingloop designated generally by the reference numeral 27. The stock entersthe recirculating loop 27 in the direction indicated by the arrows andtravels therein in a clockwise direction (FIG. 1). A delivery-flowchannel 30 forms a fluid-conducting connection 31 with the recirculatingloop 27, and a portion of the stock in the recirculating loop 27 is bledfrom the loop and into the delivery-flow channel 30, the remainingportion of the stock in the loop being recirculated.

Stock-flow-amount-varying means such as a valve 32 is mounted in therecirculating loop 27 at a location having its co-ordinate, measured inthe direction of circulation of the stock, between the connection 31between the recirculating loop 27 and the delivery-flow channel 30 andthe connection 26 between the recirculating loo 27 and the supply-flowchannel 24. In accordance with the invention, portions of the stockhaving maximum consistency are recirculated in the loop and mixed withother portions of the stock having lower consistency. In like manner,portions of the stock having minimum consistency are recirculated andmixed with other portions of the stock having higher consistency. Thevalve means 32 can be adjusted so that varying proportions of the stockare recirculated.

As FIG. shows, the stock-flow-amount-varying means need not be a valvebut may be variable impeller means such as a screw propeller 4-4 withconstant or variable pitch rotatably mounted on a propeller shaft 46 andpowered at constant or variable angular velocity by motive means such asan electric motor 48. Thus, almost any proportion, say 50% or more, ofthe stock may be recirculated, so that a given portion of the stock islikely to make several trips through the recirculating loop 49 beforefinding its way to the delivery-flow channel 50. Hence, the stock isthoroughly mixed and of uniform consistency.

Moreover, the stock in the loop is made to travel at a velocitysuflicient to assist defiocculation and prevent reflocculation anddewatering. At the same time, no harmful eddies are created.Conventional apparatus, in contrast, typically permits flocculation anddewatering or generates harmful eddies. Dewatering of a stock resultsfrom collection of water adjacent to surfaces defining the interior of atank or pipe where stock flow is slow. This collected water breaks awayfrom the surfaces and into the body of the stock from time to time andcauses a lack of homogeneity. The mixer typically employed to maintainsufficient stock velocity to prevent dewatering and flocculationgenerates harmful eddies which are evidenced by non-uniform webformation.

Flow-stabilizing means such as vanes 44, conveniently four in number,are mounted downstream of the propeller 44 is closely-spaced-apartrelation thereto to prevent the propellers imparting a helical movementto the stock. The vanes are attached along their longitudinal axes tothe wall of a portion of the loop 49 and have inner edges 44a taperingin the direction of stock flow from the Wall toward the center of thatportion of the loop. Their downstream ends 4411 are normal to thedirection of stock flow. The angle of the taper of the edges 44a isabout 15 for relatively low stock velocities (which velocities, however,should and, in accordance with the invention, can be maintainedsufliciently high to prevent flocculation and dewatering) and may be asgreat as 45 for high stock velocities. The vanes may be straight andextend parallel to the direction of stock flow or may be given a slighthelical twist in a sense opposite to the helical movement the propeller44 would impart to the stock in the absence of the vanes 44'.

All of the recirculating loops constructed in accordance with theinvention are adapted to deliver paper stock to paper-forming apparatusover a plurality of paths of unequal length. Moreover, the recirculatingloop may itself be divided into a plurality of branches of unequallength, unequal capacity, or unequal length and unequal capacity. FIG. 5shows a recirculating loop 49 having first and second branches 52 and54, the supplyfiow channel 56 intersecting the branch 52 prior to itsreunion with the branch 54. This division of the recirculating loop 49into a plurality of paths at least along a portion of the length of theloop further facilitates intimate mixing of the stock and the provisionof a stock of uniform consistency at the slice. In particular, itpermits the simultaneous smoothing out of variations in consistencygenerated at a plurality of frequencies.

The suppdy-flow channel 56 and the branch 52 meet in a base portion 57of expanding cross-sectional area so that the capacity of thereciruclating loop 49 at various points along its length in the vicinityof the base portion 57 is substantially a linear function of the volumeof stock to be transported thereby at such points per unit time.Similarly, at other convergent junctions in recirculating loopsconstructed in accordance with the invention and at divergent junctions(see, for example, FIG. 6) therein, the cross-sectional flow areas ofthe various stem and branch portions of the junctions expand andcontract as necessary to maintain the capacity of the loop at variouspoints along its length substantially a linear function of the volume ofstock to be transported by the loop at such points per unit time. Thus,stock flow through the loop is at substantially uniform velocity for agiven input of stock from the supply-flow channel 56.

The impeller means 44 may be mounted in any of several locations but ispreferably coupled with the recirculating loop 49 at a location havingits co-ordinate, measured in the direction of circulation of the stock,between the connection 53 between the recirculating loop 49 and thedelivery-flow channel 50 and the connection 59 between the recirculatingloop 49 and the supply-flow channel 56.

FIG. 6, which is a fragmentary representation of the recirculating loop49 and the supply-flow channel 50 in the region where the two meet,shows a Y-branch pipe 69. The Y-branch pipe 60 comprises three portions:a base or stem portion 62 and two branch portions. One of the branchportions 64 is a continuation of the stem portion 62 and forms with thestem portion 62 a first stock-flow path, and the other of the branchportions 66 penetrates the first stock-flow path, forming with the stemportion 62 a second stock-flow path in part coextensive with and in partdivergent from the first stock-flow path, and having an end 68positioned within the stern portion 62. The end 68 and, adjacent to theend 68, the stern portion 62 extend substantially in the same direction,and the end 68 has a blunt-lipped mouth 70 whose surface is formed of asubstance having a low coefficient of friction. A blunt leading ringformed of polytetrafluoroethylene, a material sold by the E. I. du Pontde Nemours and Co. under the trademark Teflon, may be mounted on the end68 to assure the desired low coefficient of friction.

The construction of FIG. '6 maintains stock flow at substantiallyuniform speed and permits division of the stock flow into a plurality ofseparate streams while inhibiting hang-up of the stock.

FIGS. 1 and 7 show embodiments in which the delivery-flow channels 30,'73 are connected to the recirculating loops 27, 74 with which they arerespectively associated along a considerable fraction of the length ofthe loops, and guide vanes 100, 101 to be described hereinafter aremounted relatively close to the associated recirculating loops. In FIG.1, especially, the delivery-flow channel 30 is connected to therecirculating loop 27 along a considerable fraction of the length of theloop. In FIG. 5, on the other hand, the delivery-flow channel 50 isconnected to the recirculating loop 49 along a relatively small fractionof the length of the loop, and the stock-flow guide vanes 99 are locatedrelatively remotely from the recirculating loop.

FIG. 2A shows a flow system 20 similar to the flow system 20 disclosedin FIG. 2, the principal difference being that, in the embodiment ofFIG. 2A, the bend in the delivery-flow channel 30' of the flow system 20between the loop 27 and the slice 22 is substantially eliminated, whilethe advantages of a horizontal or substantially horizontal slice and ofan inclined delivery-flow system facilitating elimination of air bubblesin the stock are retained. It is to be noted that the loop 27' is in asubstantially horizontal plane, that the flow system 20 between the loop27' and the slice 22' is inclined at a small angle, say 5 to 15, to thehorizontal, and that the wall portion 94 is continuous with the upperwall portion to which certain of the vanes 100' are attached.

This construction facilitates passage of air bubbles, which naturallymigrate upwardly in the stock, out of the loop 27', through theremainder of the flow system 20, and out the slice 22', and hencediscourages stock hang-up.

A turning-flow channel constructed in accordance with the invention forchanging the direction of movement of the paper stock from a firstdirection in a first portion of the turning-flow channel to a seconddirection in a second portion of the turning-flow channel, the first andsecond directions being different, may lie in the recirculating loop asin FIGS. 1 and 7 or may be separate therefrom as in FIGS. 3 and 5.

FIG. 3 shows a turning-flow channel 75 for changing the direction ofmovement of the paper stock from a first direction indicated by thearrows 76 in a first portion '77 of the turning fiow channel 75 to asecond direction indicated by the arrows 78 in a second portion 89 ofthe turning-flow channel 75. The first portion 77 has a cross-sectionalflow area which decreases in the direction of the arrows 76 from amaximum value in an area A to a minimum value in an area B, the maximumand minimum values being so related to each other and to energy lossesdue to friction that the horizontal components of the pressure gradientin the paper stock normal to the arrows 78 at the second portion 80i.e.,at the origin of movement of the stock in the direction of the arrows78substantially vanish. Further, the components of the pressure gradientin the paper stock in the direction of the arrows 78 at the origin ofmovement of the stock in the direction of the arrows 78 are ofsubstantially equal magnitude.

More particularly, the minimum value (which is measured at area B) ofthe crosssectional flow area of the stock in the direction of the arrows76 is 8% to 20% of the maximum value (which is measured at area A) andpreferably 8% to 15%. In tests of an eighteen-inchwide fiow systemconstructed in accordance with the invention, the minimum value was9.55% of the maximum value, and it was found that this relationshipexactly compensated for losses due to friction, so that the hori- Zontalcomponents of the pressure gradient in the paper stock normal to thearrows 78 at the origin of movement of the stock in the direction of thearrows 78 substantially vanished and the components of the pressuregradient in the paper stock in the direction of the arrows 78 at theorigin of movement of the stock in the direction of the arrows 78 wereof substantially equal magnitude. Because of these characteristics ofthe pressure gradient, the velocity of the paper stock in the directionof the arrows 78 was substantially uniform as to both to magnitude anddirection across the turning-flow channel 75 at the origin of movementof the stock in the direction of the arrows 78.

In the embodiments of FIGS. 1 and 7, the minimum value tends to begreater in comparison to the maximum value than in the case of theembodiment of FIGS. 3 and 5. That is because, in the embodiments ofFIGS. 1 and 7, the downstream end of the turning-flow channel is open topermit recirculation of the stock.

In the embodiments of the turning-flow channels shown in the drawings,the decrease in the cross-sectional flow area in the first direction (inFIG. 3, the direction of the arrows 76) is linear between the maximumand minimum values. (In flow systems larger than the eighteem inch-wideflow system referred to above, the decrease may but need not be linear.)A cross-sectional flow area is of course proportionate to the product oftwo dimensions normal to the direction of flow. The turning-flow channeltapers in two dimensions (see FIG. 2, which shows that not only the wallbut also the walls 92, .94 taper), and the wall 90 and, in FIGS. 3 and5, the wall must be curved rather than straight in order to maintain thedesired linear relationship. At the downstream end of the header, thewall 95 (FIG. 3) curves smoothly about a radius R into the wall 96 toavoid a discontinuity.

The invention also comprises a stock-flow guide vane for mounting in apaper stock flow system to facilitate turning of a paper stock from flowin one direction (which may be the second directionthe direction of thearrows 78 in FIG. 3-referred to above in connection with thetapered-flow header) at substantially uniform velocity across a crosssection of the fiow in the One direction to flow in another direction atsubstantially uniform velocity across a cross section of the flow in theother direction.

FIG. 1 shows a plurality of stock-flow guide vanes 100 constructed inaccordance with the invention. Each vane has a nose portion 102extending parallel to the second direction referred to above and a tailportion 104 extending parallel to the third direction and is adapted formounting with the nose portion 102 upstream of the tail portion 104 inthe flow system.

Each vane 100 is elongated along a first axis extending from the noseportion 162 to the tail portion 104 and narrow along a second axisnormal to the first axis and to the plane of FIG. 1. The narrowdimension of the vanes is presented to view in FIG. 2. Each vane issubstantially flat along a third axis normal to the first and secondaxes. The smallest surfaces of the vanes are presented to view inFIG. 1. Each vane has a pair of oppositely disposed sides 108, generallyparallel to the first and second axes and is curved in a plane normal tothe second axis-i.e., in the plane of FIG. l-to impart a convexity toone of the sides-the side 108 in FIG. 1- and a concavity to the other ofthe sides-the side 110 in FIG. 1. The tail portion 104 of each vane istapered to a sharp terminus 112, as shown in FIG. 2.

In the embodiment shown in FIG. 2, the terminus is a pair of edges 114,116 each forming an acute angle with the first axis and tapering to acommon point 118. This construction evens flow by providing a drag nearthe center of the channel to match the drag produced by the walls 126,128 of the channel. In the embodiment of the stock-flow guide vanes 101shown .in FIGS. 7-9, the terminus is an edge 120 normal to the firstaxis.

In the embodiment of the stock-flow guide vanes shown in FIGS. 79, thenose portion is covered with a substance 122 to discourage hang-up ofthe paper stock. The substance 122 may be polytetrafluoroethylene.

In the embodiment of the stock-flow guide vanes shown in FIGS. 3 and 4,the flow system comprises a flow channel having first and second wallportions 126, 128 opposed to each other and spaced apart from each othera distance substantially less than their width in a direction transverseof the direction of stock flow therebetween, the stock therefore havinga cross-sectional flow area of a width substantially exceeding its depthas it passes between the first and second wall portions 126, 128. Thestock-flow guide vanes are mounted in slots 129, 130 in the channelacross the width thereof alternately on the first and second wallportions 126, 128. The nose portion of each vane terminates in an edge124 forming an acute angle with the first axis and tapering towards thetail portion, and, in the same sense, away from the one of the first andsecond wall portions 126, 128 on which the vane is mounted to a point125 removed from both of the first and second wall portions 126, 128.This construction facilitates turning of the stock while inhibitinghang-up thereof. Long stock fibers, which might have a tendency tostaple over the edge 124, slide to the point 125 and thence. along thespace between the vane and the wall 126 (or 125, as the case may be).

The stock-flow guide vanes 101 shown in FIGS. 7-9 are thicker than thevanes 100 but are nevertheless substantially flat, as FIGS. 7 and 9show. A certain thickness is given the vanes 101, however, near theirupstream ends and middle portions so that a section of a vane 101 in aplane normal to the second vane axis referred to above has generally theform of a longitudinal section of a raindrop (see. FIG. 9)..Thethickness is sufficient to permit the passing of securing means 131through the vanes 101 to facilitate the securing of the Walls 132, 133together without heavy and expensive external bracing.

Thus there is provided in accordance with the invention novel and highlyeffective methods of and apparatus for delivering paper stock topaper-making apparatus, the stock being delivered at substantiallyuniform consistency and velocity. Many modifications in form and detailof the representative embodiments of the invention disclosed herein willreadily occur to those skilled in the art. Accordingly, the invention isto be construed as including all of the modifications thereof within thescope of the appended claims.

I claim:

1. In a flow system for delivering a paper stock to paper-formingapparatus, a Y-branch pipe comprising a stem portion and two branchportions, one of said branch portions being a continuation of said stemportion and forming with said stem portion a first stock-flow path andthe other of said branch portions penetrating said first stock-flowpath, forming with said stem portion a second stock-flow path in partcoextensive with and in part divergent from said first stock-flow path,and having an end positioned within said stem portion, said end and saidstem portion adjacent to said end having axes extending substantially inthe same direction and said end having a blunt-lipped mouth having asurface formed of a substance having a low-coetficient of friction.

2. A flow system for delivering a paper stock to paperforming apparatus,the flow system comprising a flow channel having first and second wallportions opposed to each other and spaced apart from each other a givendistance substantially less than their width in a direction transverseof the direction of stock flow therebetween, the stock therefore havinga cross-sectional flow area of a width substantially exceeding its depthas it passes between said first and second wall portions, and aplurality of stock-flow guide vanes mounted in said channel across thewidth thereof alternately on said first and second wall portions, eachvane (11) having a nose portion and a tail portion, (b) being (1)mountable with said nose portion upstream of said tail portion in saidflow system, (2) elongated along a first axis extending from said noseportion to said tail portion, (3) narrow along a second axis normal tosaid first axis, and (4) substantially fiat along a third axis normal tosaid first and second axes, having a pair of oppositely disposed sidesextending parallel to said second axis, and (d) being curved in a planenormal to said second axis to impart a convexity to one of said sidesand a concavity to the other of said sides, said tail portion of eachvane being formed with a pair of edges each forming an acute angle withsaid first axis and tapering to a common point and said nose portion ofeach vane terminating in an edge forming an acute angle with said firstaxis and tapering (a) toward said tail portion and, in the same sense,(b) from the one of said first and second wall portions on which saidvane is mounted to a point (1) removed from both of said first andsecond wall portions, and (2) spaced apart from said common point adistance substantially greater than said given distance.

3. A paper-stock pressure-flow system comprising a source of paperstock, a delivery-flow channel, a recircu1 lating loop having anentrance for coupling to said source in fluid-conducting relation and anexit for coupling to said delivery-flow channel in fluid-conductingrelation, means connecting the recirculating loop and said source, saiddelivery-flow channel comprising a turning flow channel for changing thedirection of movement of the paper stock from a first direction in afirst portion of said turning-flow channel to a second direction in asecond portion of said turning-flow channel, said first and seconddirections being different, said first portion having a cross-sectionalflow area which decreases in said first direction from a maximum valueto a minimum value, said maxi n o mum and minimum values being sorelated to each other and to energy losses due to friction that thehorizontal components of the pressure gradient in the paper stock normalto said second direction at the origin of movement of said stock in saidsecond direction substantially vanish and the components of the pressuregradient in the paper stock in said second direction at the origin ofmovement of said stock in said second direction are of substantiallyequal magnitude, and a plurality of stock-flow guide vanes mounted insaid second portion to facilitate turning of the paper stock from flowin said second direction at substantially uniform velocity across across section of said flow in said second direction to flow in a thirddirection at substantially uniform velocity across a cross section ofsaid flow in said third direction, each of said vanes (a) having a noseportion extending parallel to said second direction and a tail portionextending parallel to said third direction, (b) being (I) mounted withsaid nose portion upstream of said tail portion in said fiow system, (2)elongated along a first axis extending from said nose portion to saidtail portion, (3) narrow along a second axis normal to said first axis,and (4) substantially flat along a third axis normal to said first andsecond axes, (0) having a pair of oppositely-disposed sides extendingparallel to said second axis, and (0!) being curved in a plane normal tosaid second axis to impart a convexity to one of said sides and aconcavity to the other of said sides, and said tail portion beingtapered to a sharp terminus.

4. A flow system for delivering a paper stock to paperforming apparatus,the flow system comprising a supplyfioW channel for transporting thepaper stock, a recirculating loop, said recirculating loop and saidsupply-flow channel having a fluid-conducting connection with eachother, a delivery-flow channel, said recirculating loop and saiddelivery-flow channel having a fluid-conducting connection with eachother, a screw propeller coupled with said recirculating loop forvarying the amount of the stock which is recirculated, andflow-stabilizing means mounted in said loop for preventing theacquisition by said stock of a helical motion due to the action of saidpropeller.

5. A stock-flow guide vane for mounting in a paperstock flow system tofacilitate turning of a paper stock from flow in one direction atsubstantially uniform velocity across a cross section of said flow insaid one direction to flow in another direction at substantially uniformvelocity across a cross section of said flow in said other direction,the vane (at) having a nose portion covered with a substance todiscourage hang-up of said paper stock and a tail portion tapering to asharp terminus, (b) being (1) mountable with said nose portion upstreamof said tail portion in said flow system, (2) elongated along a firstaxis extending from said nose portion to said tail portion, (3) narrowalong a second axis normal to said first axis, and (4) substantiallyflat along a third axis normal to said first and second axes, (0) havinga pair of oppositely disposed sides extending parallel to said secondaxis, and (d) being curved in a plane normal to said second axis toimpart a convexity to one of said sides and a concavity to the other ofsaid sides, a section of said vane in a plane normal to said second axishaving generally the form of a longitudinal section of a raindrop.

6. A stock-flow guide vane as defined in claim 5 in which said substanceis polytetrafiuoroethylene.

7. In apparatus for facilitating turning of a paper stock from flow inone direction at substantially uniform velocity across a cross sectionof said flow in said one direction to flow in another direction atsubstantially uniform velocity across a cross section of said flow insaid other direction, the improvement comprising a plurality of vanesmounted in parallel relation, each vane (a) having a tail portlontapering to a sharp terminus and a nose portion, (b) being (I) mountedwith said nose portion upstream of said tail portion in said flowsystem, (2) elongated along a first axis extending from said noseportion to said t l E Z iQ 3) narrow along a second axis normal to" 9said first axis, and (4) substantially flat along a third axis normal tosaid first and second axes, (0) having a pair of oppositely disposedsides extending parallel to said second axis, and (d) being curved in aplane normal to said second axis to impart a convexity to one of saidsides and a concavity to the other of said sides.

8. A stock-flow guide vane as defined in claim 7 in which said terminusis an edge normal to said first axis.

9. A stock-flow guide vane as defined in claim 7 in which said terminusis a pair of edges each forming an acute angle with said first axis andtapering to a common point.

10. A stock-flow guide vane as defined in claim 7 in which a section ofsaid vane in a plane normal to said second axis has generally the formof a longitudinal section of a raindrop.

11. A stock-flow guide vane as defined in claim 7 in which said noseportion terminates in an edge forming an acute angle with said firstaxis.

References Cited OTHER REFERENCES Gavelin: Fourdrinier Papermaking,Lockwood Trade Journal Co. Inc., New York (1963), pp. 43-45, copy inGroup 170.

Keller: The Manifold Problem, Journal of Applied Mechanics, March 1949,pp. 77-85.

S. LEON BASHORE, Primary Examiner. J. H. NEWSOME, Assistant Examiner.

4. A FLOW SYSTEM FOR DELIVERING A PAPER STOCK TO PAPERFORMING APPARATUS,THE FLOW SYSTEM COMPRISING A SUPPLYFLOW CHANNEL FOR TRANSPORTING THEPAPER STOCK, A RECIRCULATING LOOP, SAID RECIRCULATING LOOP AND SAIDSUPPLY-FLOW CHANNEL HAVING A FLUID-CONDUCTING CONNECTION WITH EACHOTHER, A DELIVERY-FLOW CHANNEL, SAID RECIRCULATING LOOP AND SAIDDELIVERY-FLOW CHANNEL HAVING A FLUID-CONDUCTING CONNECTION WITH EACHOTHER, A SCREW PROPELLER COUPLED WITH SAID RECIRCULATING LOOP FORVARYING THE AMOUNT OF THE STOCK WHICH IS RECIRCULATED, ANDFLOW-STABILIZING MEANS MOUNTED IN SAID LOOP FOR PREVENTING THEACQUISITION BY SAID STOCK OF A HELICAL MOTION DUE TO THE ACTION OF SAIDPROPELLER.
 7. IN APPARATUS FOR FACILITATING TURNING OF A PAPER STOCKFROM FLOW IN ONE DIRECTION AT SUBSTANTIALLY UNIFORM VELOCITY ACROSS ACROSS SECTION OF SAID FLOW IN SAID ONE DIRECTION TO FLOW IN ANOTHERDIRECTION AT SUBSTANTIALLY UNIFORM VELOCITY ACROSS A CROSS SECTION OFSAID FLOW IN SAID OTHER DIRECTION, THE IMPROVEMENT COMPRISING APLURALITY OF VANES MOUNTED IN PARALLEL RELATION, EACH VANE (A) HAVING ATAIL PORTION TAPERING TO A SHARP TERMINUS AND A NOSE PORTION, (B) BEING(1) MOUNTED WITH SAID NOSE PORTION UPSTREAM